The present invention concerns a detergent composition with a high content of anionic tensides that is characterized by a granule structure resistant to mechanical or unfavorable climatic influences and is especially suitable for washing textiles and other solid surfaces by hand. Such agents lend themselves particularly well for use in developing countries, where laundering is done under still relatively simple conditions, such as in the tub and without additional heating.
Detergent compositions used in such cases must meet a number of special requirements. Since, in the route from the producer to the consumer, these detergent compositions are not infrequently repackaged several times and are usually transported via long and often imperfect shipping routes, the mechanical resistance of the granulate must meet more stringent requirements. The mechanical resistance and free-flowing quality must be retained even under unfavorable climatic conditions, especially in areas of high relative humidity of the air. The detergent compositions should be suitable not only as single detergents but also combinable and compatible with additives conventionally used and easily available in the respective consumer country, for example, such as soap powder, bleach and similar substances, and the granule structure must largely remain intact also during a mixing process carried out under less than optimal conditions, and it must be formulated to prevent separations during further transporting of the products. On the other hand, the granules should break up quickly when added to cold water and dissolve after brief stirring, despite their mechanical resistant quality.
An inadequately informed consumer, possibly an illiterate, usually judges the action of a detergent by the foam developed and regulates the amount to be used accordingly, which is the reason for the preferability of high-sudsing substances to prevent the use of excessive amounts and the environmental damage resulting from it. Consequently, nonionic tensides are less suitable for this purpose of washing by hand because of their low foaming tendency, especially since they have the characteristic of removing the oils from the skin to a particularly efficient degree and leave an unpleasant feeling on the skin.
Detergent compositions consisting of compact granules and surfactants incorporated in them are known, for example, for German published Application DE-OS No. 25 36 594 and U.S. Pat. No. 4,269,722. These are socalled carrier granules that are produced by spray-drying or shaping without an addition of detergent and then charged with liquid or molten nonionic tensides. The process requires several procedural steps and is relatively expensive. Such a process is not suitable for the saltlike anionic tensides. Such prior art powders also have a very compact granule structure and a comparable high bulk density exceeding 500 gm/l, usually 600 to 800 gm/l. However, such dense detergent granules with a high specific weight dissolve only very slowly in cold or moderately warm water. Since they, in contrast to less dense spray-dried powders, sink immediately to the bottom in the wash water, a sediment forms in the wash tub when they are used and this dissolves completely only after prolonged stirring. In such cases, it is also very difficult to judge at what point the dissolving process is completed.
The preparation of granular detergents by spray-drying is also known, but the spray-drying of conventional formulations generally produces relatively soft, loose powders with spherical structure. Their bulk density lies generally definitely below 500 gm/l and is usually 200 to 350 gm/l. This type of powder, which is normally produced by spraying an aqueous detergent slurry under high pressure through stationary jets, does have optimal dissolving characteristics, but its resistance to mechanical stress is relatively low. Older drying equipment with rotating spray jets do produce a more compact but very much smaller granule with a high proportion of dust. Such powders have a strong tendency to clump together and have unfavorable pouring characteristics. Also problematical is the spray-drying of detergents with a high content of organic substance, i.e., exceeding 40%, at the usually high drying temperatures in the spray-drying towers because of the danger of dust explosions and autoxidation processes that can result in the browning of the powder.